Methods of heel attaching



March 21, 1961 J. F. LEAHY METHODS OF HEEL ATTACHING Filed April 27, 1959 [nvenor James F Lea/'1y B h' @y Unite States arent Machinery Corporation, Fiernington, NJ., a corporation of New Jersey rasa apr. 27, 1959, ser. Ne. essere e claims. (ci. 12-r47) This invention relates to attachment of heels to shoes and particularly to a method for attaching heels to womens shoes in a manner giving extra firmness to the slices.

The usual method of attaching heels to womens shoes is by nails orscrews which mustbe inserted by complicated and expensive machinery. The inner surface at the heel of a shoe becomes progressively more irregular and uncomfortable as the shoe is Worn due to the irregular undersupport in this area. Also, and particularly with currently` fashionable, narrow, thin heels, great difliculty has been encountered in the splitting and breaking of heels when mechanical fastenings are driven.

lt has been proposed,` see United States Letters Patent 2,447,512, granted August 24, `l948,.in the name of l ames F. .e`ahy, to attach a heel by forcing heat-softened plastic through an opening in a heel to create a plastic union between heel and shoe. In the method of the patent it was found important to shape the heel and shoe upper to provide mechanical interlocks between the plastic andthe heel and heel seat respectively.` Also, the heel was weakened by the opening required for injecting plastic. Special clamps and jigs were required to hold the shoe bottom and heel in tight relation against the injection pressure necessary to secure complete filling of spaces and bonding of surfaces; and premature cooling and stiifening of the plastic created further problems.

It is au object of the present invention to provide a simple method of attaching a heel to a shoe upper in a manner giving superior firmness to the whole shoe. It is a further object of the invention to provide a heel attaching method requiring a minimum of equipment and involving a minimum hold up in .the passage of shoes along a production line.

I have found that heels may be strongly and firmly l attached to shoe uppers by modifying the heel to provide a greater than normal enclosed space when the heel and upper are assembled, introducing an expandable curing `liuid resinl composition in the space and expanding and curing the resin to iill the space, bond to the surfaces defining the space and become hard.

The invention will be described more fully in connection with the attached drawings forming part of the disclosure, in which:

Fig. l is an angular View of a heel and of the back part of a `shoe before attaching the heel;

Fig. 2 is an elevational View with parts broken away of a shoe with a heel attached by expanded resin according to the presentmethod; and

Fig. 3 is an angular view of another form of heel suitablefor heel attaching by the present method.

in accordance with the present invention, a body of a fluid, expandable, hardenable resin, preferably a polyurethane resin, composition is deposited in a recess or cavity 12 in the heel seat engaging surface 14 of a heel 1d. The heel 16 is thereafter assembled against the heel seat 18 of a shoe upper 2|)y and the resin 10 is caused to expand to fill the recess 12 and the space 22 between the heel seat engaging surface -14 and heel seat 18 and to wet and adhesively bond to the surfaces 14 and 18 of the heel and heel seat which define the space 22. The resin is then hardened to create a strong, rigid, unitary structure of heel and shoe.

The heel 16, is shown inFig. l, is formed with an annular recess 12 in the heel seat engaging surface 14, the remainder of the heel seat engaging surface corresponding to the usual contour of such surface and Haring outwardly toward the edge portions 24 of the heel. The outwardly flaring surface provides a substantial area for bonding by the expanded resin to link ythe heel 1d to the shoe upper 20.

The shoe upper 20 is of conventional design withthe sole 26 terminating in the vicinity` of the heel breast. A steel shank stiifener 28 extends beyond the sole A2.6 into the heel seat portion 18 of the shoe upper so that it is embedded in the expanded resin in the space 22 between the heel 16 and heel seat 13 (see Fig. 2).` The overlasted margin 30 of the shoeupper 20 is secured bylasting tacks 32 which are driven around the rim of the heel seat 18 in conventional manner. This marginal area 3i!4 provides an advantage to the bonding action of the expanded resin by offering many smallrecesses around the tacks and the crevices formed in lasting the shoe to receive and hold the resin.

Satisfactory bonding of the surfaces of the heel seat and heel seat engaging surface of the heel requires that the surfaces 14 and 18 be fully wet by the resin. Wetting contact between the surfaces and the expandngresin effects a limited breakdown of the resin cells and it is important that the resin foam briskly and supply sutiicient resin to replace the resin foam broken down by such contact. rl'he fluid resin of the broken foam effects thorough wetting of surfaces to give substantial areasof bond as distinguished from contact only with the surfaces of the foam bubbles. Also the fluid resin penetrates porous fibrous components of the heel seat so that the union between the resin and the brous material cannot be ruptured by simply peeling off the surface fibers of the iibrous material.

Effective and uniform wetting of the fibrous surfaces of the heel seat 18 is secured where the resin contacting the fibrous surfaces is a uniformly expanded foam. The reaction to form a polyurethane resin foam goes through a series of stages. Initially the resin increases in viscosity and develops a milky look without noticeable increase in volume. Thereafter the resin begins to expand somewhat irregularly at iirst and then rapidly and uniformly. Freshly expanded polyurethane foam is tender and the bubbles will collapse when lightly pressed; and it is only after expansion is complete and a further curing or reaction period that the resin foam gains mechanical strength.

In the present method Where the body 10 of reactive mixture is placed in a fairly deep recess 12 in a heel 16 to be attached, the earlier stages of .the resin foam reaction take place While the mixture is within the recess 12. By the time the mixture has expanded to lill the recess, foam formation is rapid and uniform.

The heel 16 with reactive mixture in the recess 12 is assembled againstthe heel seat 1S ofa shoe upper 2li before substantial foaming and is held by suitable means snugly against the heel seat 1S until foaming and curing `of the resin are complete. As shown in Fig. 2, the edge portions 24 of the heel 16 are pressed against the edge portions 30 of the heel seat 18 of a shoe upper 21d to form a duid-tight joint around the space 22 defined by the surfaces of the heel seat 18 and the heel 16.

Strong union between the heel 16 and the heel seat 13 is obtained by iilling the entire space between them with resin out -to the thin wedge-like spaces at the edges.

But the heel seat 18 of a shoe upper 20 is necessarily irregular. As shown in Figs. 1 and 2, the irregular thickness and extent of the overlasted margins 30 of the Y shoe upper materials and the arrangement of the shank stiffener 28 are among the factors contributing to this irregularity. As a result the volume of the space 22 enclosed between the heel seat 18 and the heel seat engaging surface 14 of a heel will vary widely from shoe Vto shoe. However, by using heels formed with uniform recesses 12 in the heel seatengaging surface 14, a ballast effect is secured. That is, where the volume of f the recess 12 is substantial, for example at least about equal to and preferably from 1 to 10 times the average volume of the space 22, fairly large percentagewise variations in the volumes of the spaces 22 in different shoes Will'amount to only very small percentagewise variations in total free space, that is, in the sums of the space 22 and the volume ofthe recess 12. This factor enables metering of a determined quantity of expandable resin mixture for each shoe to effect complete lling of the Space 22 without development of such pressures as would cause leakage of resin from the joint between the heel 16 and the heel seat 18. It will be understood that with broad base heels, the recess may be made so large that the heel is in effect only a shell which is reinforced by oam formed therein andv secured to the shoe by the same The heel 16 may be held against the heel seat 18 by suitable means such as clamps or jigs (not shown). However, since as noted, the present method can be practiced without development of high pressure in the fenclosed space 22, it is preferred to hold the heel 16 against the heel seat 18 by a simple mechanical fastening 34 such as a nail driven through the heel seat 18 'into the heel 16.

In the heel 16 shown (see Figs. 1 and 2), there is provided a central portion 36 at the general level of the heel seat engaging surface 14 of the heel. This portion 36 provides a body of suitable dimension to receive and strongly hold a driven fastener 34 to hold the heel 16 against the heel seat 18. The fastener 34 which may be of the nature of a Stronghold nail with a moderate head extends down through the insole 38 at the heel seat 18, 'through an opening 40 in the rear end of the shank stiffener 28 and into the central portion 36. The head of the fastener 34 engages the insole 38 which is slightly flexed to exert a resilient -pull through the fastener 34 to hold the heel 16 resiliently against the heel seat 18 of the shoe.

The nail 34 holds the shank stiffener 28 and heel seat 18 firmly against the central portion 36 of the heel seat engaging surface 14 of the heel 16. The expanded resin fills in all crevices in and around the shank stiffener 28 and between the central portion 36 and the heel seat 18 and also penetrates, wets and fills the irregularities and crevices between the heel seat 18 and the flaring portion of the heel seat engaging surface 14 to create a strong bond well spaced from the neutral axis of the area between the heel 16 and heel seat 18. The resultant combination is mechanically efficient to create va strong, rigid union of the heel 16 to the heel seat 18 of the shoe upper 20. Also, since all spaces between the heel 16 and heel seat 18 are filled with the strong foam, the heel seat 18 is not distorted by the stresses encountered in wearing the shoe and over-all support for the Wearers heel is provided throughout the life of the shoe.

The Aheel seat engaging surface 14 of the heel may have a variety of contours subject to the requirement that it be formed with a recess or recesses 12 providing approximately balanced volumes on each side of the central portion 36 of said heel. Balanced volume is important to insure uniform supply of foam to all portions of the enclosed space 22 and into wetting contact with all surfaces in the space enclosed between heel 16 and heel seat 18.

In the :heel 16' shown in Fig. 3, separate recesses 12' are formed in the heel seat engaging surface 14 of the heel. These recesses 12' are approximately equal in volume and are separated by a central bar 36', the surface of the bar conforming approximately to the corresponding surface of a conventional heel without recesses. This bar member 36 reinforces the heel from front `to back and also provides a surface of sufficient area t0 receive and hold a nail to secure the heel firmly against the heel seat of a shoe during the course of expansion and curing of resin foam.

A wide variety of foamable resiuous compositions are known which will expand and cure to a firm strong condition bonding firmly to surfaces. It is preferred to use reactive mixtures forming rigid polyurethane foam. A suitable reactive mixture comprises a so-called prepolymer, suitably a reaction product of a liquid polyester and a polyisocyanate, together with water and a catalyst. Combinations of reactants for forming strong rigid foams are known and a variety 'of useful formulations can be compounded by theskilled chemist. It has been found desirable touse a reactant mixture which will give a foam which after curing in the recess 12 and space 22 will have a density of from about 6 to l5 pounds per cubic foot; but it is to be remembered that limited foam break-down occurs in the course of filling the irregular spaces and that foam compositions giving a much lower density on free expansion, i.e. as low as two or .three pounds per cubic foot may provide a desirable foam density when used inthe present process.

The mixture reactive to generate foam is ordinarily introduced into the recess as a liquid. However, the mixture may be cooled to a temperature at which reaction does not take place, -for example by pouring onto solid carbon dioxide (Dry Ice), which will solidify the mixture. This cold solidified mixture may be kept in cold condition until needed and introduced into the heel recess as pellets or granules which melt and then react to generate the required foam.

The following example is given to aid inunderstanding the invention but it is to be understood that the invention Ais not restricted to the materials, proportions or procedure set forth therein except yas required by the appended claims.

Example parts by weight of tolylene diisocyanate was mixed thoroughly with 20 parts of a polyester formed by esterification and polymerization of one mol of adipic acid, one mol of ethylene glycol and 2 mols of trimethylolpropane, the polyester having a hydroxyl value of from 350 to 40() and an acid number of 2. The mixture was stirred thoroughly and reaction to form a prepolymer occurred as evidenced by an increase in temperature.

A catalyst mixture was prepared comprising parts by weight of the same polyester, one part by weight of N-methyl morpholine, 3 parts by weight of water and one part by weight of a nonionic emulsifier.

A shoe upper 20 was lasted and a shank stiffener 2S and a sole 26 were applied, the sole 26 terminating in the vicinity of the heel breast of the shoe upper. The last was then removed from the shoe upper.

parts by weight of the prepolymer were combined with 75 parts by weight of the catalyst mixture and a portion of the resultant mixture was promptly filled in around the bottom of the circular recess 12 in the heel seat engaging portion 14 of a heel 16. The recess had a volume of about 3 cc. The heel 16 was then assembled against the heel'seat 18 of the shoe upper with the edge portions 24 of the heel 16 snugly engaging the edge portions 30 of the heel seat 18 to form a fluid-tight joint. A nail 34 was driven through the heel seat portion of the shoe into the central portion 36 surrounded by the recess 12 to hold the heel 16 firmly against the shoe upper 20. The resin mixture in the recess developed foam to iill the recess 12 and then to flow out into the narrow spaces 22 between the heel seat 18 and the heel 16. The shoe was allowed to stand overnight and tested. The heel and shoe upper were found to be rigidly joined together as an integral unit and the heel could not be removed without rupture of the attaching surfaces of the shoe upper.

Having described my invention, what l claim as new and desire to secure by Letters Patent of the United States is:

1. The method of permanently attaching a heel to a shoe which comprises providing a shoe upper and a heel formed with a recess in the heel seat engaging surface,

depositing in said recess a quantity of a liquid mixture reactive to expand and cure to a stii, strong resin foam, said quantity of reactive mixture being sufiicient to produce on expansion a volume of foam at least equal to the sum of the volume of said recess and the volume of space which would be enclosed between the heel seat engaging surface of a conventional heel for said shoe and the heel seat of said shoe, placing said heel against said heel seat, holding said heel in place against said heel seat and causing said mixture to react to form resin foam to fill said recess and space enclosed between said heel and heel seat and to harden to a rigid body uniting the heel and shoe into a unitary structure.

2. The method of permanently attaching a heel to a shoe which comprises providing a shoe upper and a heel formed with a recess in the heel seat engaging surface, depositing in said recess a quantity of a liquid mixture reactive to expand and cure to a stiff, strong polyurethane resin foam, said recess having a volume of from 1 to 10 times the volume of the space which would be enclosed between the heel seat of said shoe upper and the heel seat engaging surface of a conventional heel for said shoe upper, said quantity of reactive mixture being sufficient to produce on expansion a volume of foam at least equal to the sum of the volume of said recess and the volume of said space, placing said heel against said heel seat, holding Said heel in place against said heel seat and causing said mixture to react to form stiff, strong polyurethane resin foam to lill said recess and space enclosed between said heel and heel seat and to harden to a rigid body uniting the heel and shoe into a unitary structure.

3. The method of permanently attaching a heel to a shoe which comprises providing a shoe upper and a heel formed with a recess in the heel seat engaging surface, depositing in said recess a quantity of a liquid mixture reactive to expand and cure to a stiff, strong polyurethane resin foam, said recess having a volume of from 1 to 10 times the volume of the space which would be enclosed between the heel seat of said shoe upper and the heel seat engaging surface of a conventional heel for said shoe upper, said quantity of reactive mixture being effective to produce on expansion a volume of foam at least equal to the sum of the Volume of said recess and the volume of said space, placing said heel against said heel seat and securing said heel in place by driving a mechanical fastening through said heel seat and into said heel in a central portion adjacent said recess to hold said heel against said heel seat, and causing said mixture to react to form stilf, strong polyurethane resin foam to ll said recess and space enclosed between said heel and heel seat and to harden to a rigid body uniting the heel and shoe into a unitary structure.

4. The method of permanently attaching a heel to a shoe which comprises providing a shoe upper and a heel formed with a recess in the heel seat engaging surface, said recess being formed to provide substantially balanced volumes on opposite sides of a central portion of the heel seat engaging surface and said central portion having a surface at the general level relative to the heel as a similar portion of the heel seat engaging surface of a conventional heel and having a dimension to receive and hold a driven fastener, depositing in said recess a quantity of a liquid mixture reactive to expand and cure to a stiff, strong polyurethane resin foam, said recess having a volume of from 1 to l0 times the volume of the space which would be enclosed between the heel seat of said shoe upper and the heel seat engaging surface of a conventional heel for said shoe upper, said quantity of reactive mixture being effective to produce on expansion a volume of foam at least equal to the sum of the volume of said recess and the volume of said space, placing said heel against said heel seat and securing said heel in place by driving a mechanical fastening through said heel seat and into said central portion of said heel to hold said heel against said heel seat, and causing said mixture to react to form stiif, strong polyurethane resin foam to ll said recess and said enclosed space and to harden to a rigid body uniting the heel and shoe into a unitary structure.

5. The method of permanently attaching a heel to a shoe which comprises providing an overlasted shoe upper and a heel formed with a recess in the heel seat engaging surface, said shoe upper having a sole terminating in the vicinity of the heel breast and a shank stiffener with portions extending beyond the sole into the heel seat portion, said recess being formed to provide substantially balanced volumes on opposite sides of a central portion of the heel seat engaging surface and said central portion having a surface at the same general level relative to the heel as a similar portion of the heel seat engaging surface of a conventional heel and having a dimension to receive and hold a driven fastener, depositing in said recess a quantity of a liquid mixture reactive to expand and cure to a stiff, strong, polyurethane resin foam, said recess having a volume of from 1 to 10 times the space which would be enclosed between the heel seat of said shoe upper and the heel seat engaging surface of a conventional heel for said shoe upper', said quantity of reactive mixture being effective to produce an expansion in volume at least equal to the sum of the volume of said recess and the volume of said space, placing said heel against said heel seat with portions of said shank stiifener between said central portion and said heel seat and securing said heel in place by driving a mechanical fastening through said heel seat and into said central portion of said heel to hold said heel against said heel seat, and causing said mixture to react to form stiff, strong, polyurethane resin foam to fill said recess and said enclosed space and to surround said portions of the shank stiffener, and to harden to a rigid body uniting Ithe heel, shank stilener and shoe into a unitary structure.

6. The method of permanently attaching a heel to a shoe which comprises providing a shoe upper and a heel formed with a recess in the heel seat engaging surface, depositing in said recess a quantity of a frozen, normally liquid mixture reactive to expand and cure to a stiff, strong polyurethane resin foam, said recess having a volume of from l to l0 times the volume of the space which would be enclosed between the heel seat of said shoe upper and the heel seat engaging surface of a conventional heel for said shoe upper, said quantity of reactive mixture being suicient to produce on expansion a volume of foam at least equal to the sum of the volume of said recess and the volume of said space, placing said heel against said heel seat, holding said heel in place against said heel seat and raising the temperature of said mixture to cause said mixture to react to form still?, strong polyurethane resin foam to lill said recess and space enclosed between said heel and heel seat and to harden to a rigid body uniting the heel and shoe into a unitary structure.

Ushakoff i Oct. 20, 1942 Joiner et al. Sept. 1, 1959 

